the moment at which someone (or something) who has been consistently dependable suddenly collapses or disintegrates, due to age or any other factor

this phrase was popularized (and perhaps created) by Bill Simmons of ESPN as a candidate to replace jump the shark, it references the decline of the NBA's Gary Payton which became shockingly apparent in the 2004 NBA playoffs

Before marrying my girlfriend, my intuitions warned me that her libido eventually will go GP on us.